Follow-up type pressure fluid servomotor



Patented July 4, 1950 "UNITED STATES PATENT OFFICE FOLLOW-UP TYPE PRESSURE FLUID SERVOMOTOR William-H. Newell, New York,-N. Y., assignor to The Sperry Corporation, a corporation of Delaware 1 Claim.

This invention relates to a novel and improved hydraulic follow-up system and more particularly to a-servomotor construction. This applicationis a division of the co-pending application of William H. Newell, Serial No. 594,288, filed May 17, 1945', for Hydraulic Follow-up System, which in turn is a division of an application of Newell .et al., Serial No. 534,330, filed May 5, 1944, for Automatic Gun Control System.

Anobject of the invention is to provide a servomotor of the above type having novel and improved details of. construction and features of operation.

Although the novel features which are believedto: be characteristic of this inventionare pointed out more particularly in the claim appended hereto, the nature of the invention will be better understood by referring to the following description; taken in conjunction with the accompanying drawing in which a specific embodiment thereof has been set forth for purposes of illustration.

In the drawing the figure .is a diagrammatic View of a servomotor embodying the present invention.

Referring tothe drawing, the servomotor block 2l0 is shown as containing train servomotor 220, elevation servomotor 22! and a P1 generator valve 222 which is designed to generate. a fixedpressure P1.

The pressure P1 is supplied by a P1 generator valve 222 formed in the block 2l0 and'cornprising a chamber having a slide 56 provided with end surfaces 51' and- 58' forming end chambers 59' and 60', respectively. The end sur- 2 face 51' is formed with one-half of the area of the end surface 58' so that when the slide 56 is in balanced position the pressure within the chamber 60' will be half that within the chamber 59.

The chamber 59' is connected to the duct 20'! containing fluid under pressure P2 by means of a passage 223. The slide 56 is formed with an annular chamber 63' which communicates through a passage 225 with the chambers 232 and 232 to supply fluid under the pressure P1 thereto. The annular chamber 63' communicates with the chamber 60 by means of a passage 65' in the slide. v

The slide 56 is provided with a reduced diameter end portion 10 terminating at the surface 51' above mentioned and has an annular end surface H surrounding the end portion 10. This annular surface II forms with an intermediate end wall of the valve chamber an annular chamber 12'. The annular chamber 12 communicates through a passage 224 with the passage 255 containing fluid under return pressure P0.

Fluid under pressure P2 is supplied to the i the sleeve 23B.

chamber 59 of the generator valve 222 from the P2 supply duct 48 through a duct 26'! and a passage 223. Return fluid at a pressure Pois fed tothe return duct 50 from'the valve chamber 12' through a passage 224 and a duct 205. Fluid under pressure P1 is supplied from the valvechamber 60 to a passage 225.

The elevation servomotor 22l comprises a chamber'formed in the valve block 2."), containing a sleeve 230 anda slide. valve 23! which ismounted for axial movement within the:sleeve 230. Chambers 232 and 233 are formed at the twoends of the sleeve 230. The chamber 232 is supplied with fluid at pressure P1 through a passage 234which communicates with thepa-ss sage 225. Chamber 235 is supplied with fluid at a pressure controlled by the operationuof the slide valve 23! througha passage 235'communi eatin with an elongated! chamber 236 in the sleeve 230.

The slide valve 23! is acted upon at one end :by the hydraulic pressure P1 from the chamber 232 and at its other end forms a closure for a chamber 237- formed within the bore of The slide valve 23] is acted upon by two opposed springs 238 and 239. The spring 238 extends between one end of the slide valve:23.l and. a ring 243 attached t the sleeve 23!) within the chamber 23?. The spring 239 extends between the opposite end of the slide valve 23I and a pin 24! which is mounted ln'a fixed plate 242 forming an end enclosure for the chamber 232. The pin 24! is adjustableior varying the tension of the spring 239. The slide valve '23l is for-med with a central annular chamber 245 which communicates through a passage 246- in the sleeve 23!] with the chamber 236 and is thus in communication with end chamber- 233.

Fluid under pressure P2 is supplied through-a passage 250 from a passage 25L which communicates with the duct 201, to an elongated chamber 252 formed in the sleeve 230 and thence to a passage 253 which terminates adjacent the lower end of the chamber 245 and is normally closed by the slide valve 23 l.

Fluid at the pressure P0 is returned from the valve 22! to the return duct 255 through apassage 255 in the valve block 2"], which passage is connected to the slide valve 23-lthrough a passage 255 in the valve block 210 leading to an elongated chamber 25'! in the sleeve 230, thence through a passage 258 in the sleeve 230 which passage terminates adjacent the upper endrof the chamber 245 and is normally closed by the slide valve 23L The passages 253 and 2.58 are so arranged that one or the other is brought into communication with the chamber 245 when the slide. valve 23| moves axially from its balanced position.

Fluid under pressure'Pe is supplied from duct 3 3| through passage 260 in the valve block 2!!! to an elongated chamber 26! in the sleeve 230, thence through a passage 262 in the sleeve 23!) which communicates with the chamber 231.

The link 366 which connects to the automatic computing apparatus is connected to the sleeve and extends outwardly from the valve block The speed of response of the sleeve 230 to movements of the valve 23! is controlled by an adjusting screw 265 which extends into the passage 235 and controls the flow of fluid therethrough. Thus the controlling effect on the sleeve 23!] of sudden changes in the controlling pressure may be eliminated to a large extent by the restricted flow through the passage 235. A stop screw 266 carried by the sleeve 23!) extends into'the chamber 245 to limit the axial movegiant of the slide valve 23! relative to the sleeve Assuming that the pressure of Fe equals the pressure P1, then the pressure within the cham-- ber 23'! will equal the pressure in the chamber 232 and the forces on the two ends of the slide valve 23! will be balanced. The valve will then take a position at which the forces due to the springs 238 and 239 are also balanced and the sleeve 230 will be in a position relative to the slide'valve 23! such that the passages 258 and 253 are both closed, as shown in the drawing.

If now the pressure Fe is assumed to increase, the pressure in chamber 23'! becomes greater than the pressure (Pi) in chamber 232 and the slide valve 23! is caused to move downwardly thereby increasing the tension of spring 238. This downward movement of the slide valve 23! opens the passage 253 to the chamber 245 and allows fluid under pressure P2 to pass from the passage 25!) through the chamber 245 and the passage 235 to the chamber 233. This increases the pressure in the chamber 233 and causes the sleeve 23!] to move downwardly. This action continues until the downward movement of the sleeve 23!] with respect to the slide valve 23! again centers the sleeve with respect to the valve and closes the passage 253. As the sleeve 23!] thus follows the movement of the valve 23!, the tension of the spring 238 is restored to normal. The valve 23! and the sleeve 23!! move down together, except for the effect of the restriction in passage 235 caused by the screw 265, until the tension of the spring 239 is reduced by an amount corresponding to the increase in the pressure Fe in chamber 231. Since the pressure in the chamber 232 and tension of the spring 238 remain at their normal values, the valve 23! and the sleeve 230'assume a position where the increased effect of the pressure in chamber 23'! tending to move the valve 23! down is neutralized by the reduced effect of the spring 239.

The sleeve 230 accordingly not only follows the movement of the slide valve 23!, but, due to the large area of the end of the sleeve 230 as compared to the area of the ends of the slide valve 23!, exerts an increased force which may be applied by the link 366 to the input of a computin mechanism such as that set forth in the patent applications above identified. The ratio of the force exerted by the link 366 to that exerted upon the slide valve 23! may be varied as desired by changing the relative dimensions of the parts Hence, the sleeve 23!) may be caused to exert any necessary force upon the link 366 for actuating the computing mechanism. I 1

As explainedthe movement of the slide'valve 23! and the sleeve 236 is proportional to the changes in pressure Pe. the link 366 represents the rate of elevation dE which is to be set into the computing mechanism.

It will be noted that the position taken by the link 366 is dependent only upon the pressure Pa and is not affected by leakage in the hydraulic system provided the leakage does not change the pressures. For any given control pressure Pe there is an exact corresponding position for the link 366 which is determined by the spring and hydraulic pressures only, provided of course the hydraulic system has sufiicient capacity to keep the various passages and ducts full at the various pressures.

The elements of the train servomotor 220 are identical with those of the elevation servomotor above described and have accordingly been given the same reference characters with the suffix t. Fluid under pressure Pt is supplied to the train rate amplifier valve from the duct 8!! through a passage 27!? in the valve block 210.. This. causes a movement of the slide valve 23! which is proportional to changes in pressure Pt and a corresponding movement of the sleeve 230 which actuates the link 355 to introduce the rate of train dBs into the computing mechanism.

Although a specific embodimentof the invention has been shown for purpose of illustration, it is to be understood that the invention is capable of various adaptations as will be readily apparent to a person skilled in the art. The invention is only to be limitedin accordance with the scope of the following claim.

What is claimed is:

A pressure responsive servomotor comprising ahpusing, a piston in said housing forming a fluid chamber at each end of the housing, a bore in the piston communicating at one end with the corresponding end chamber and closed at the other end, a slide valve in said bore, springs extending between the ends of said slide valve and the closed end of said bore and said housing, respectively, a passage supplying fluid at a fixed intermediate pressure to the end chamber communicating with said bore so as to applyforce to said piston and to said slide valve, a passage supplying control pressure to the chamber formed between the other end of said slide valve and the closed end of said bore to displace said slide valve from its mid-position against the force of said springs, passages in said piston containing fluid under high and low pressures, respectively, terminating in ports closed by said slide valve, a passage in said piston communicating with the chamber at the other end of said piston, said slide valve having means establishing communication between said last passage and said high or low pressure passages, respectively, in response to displacement of said slide valve relative to 'said piston so as to establish a pressure in said last chamber to cause said sleeve to follow said slide valve, and a link actuated by said piston.

WILLIAM H. NEWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,600,376 Trotter Sept. 21, 1926 1,822,445 lVlarsland Sept.

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